Dermatology: Practical and Conceptual Original Article | Dermatol Pract Concept. 2025;15(3):5382 1 Impact of Lidocaine Concentration on Analgesic Efficacy and Adverse Events in Dermatologic Infiltrative Anesthesia Thanh Le Thai Van1,2, Thong Nguyen Tri1, Hung Ta Quoc1, Tuan Ngo Anh1, Yen Thai Thanh1, Thao Nguyen Phuong1, Anh Le Vi1, Nam Tran Ngoc Khanh1, Vy Tran Hanh1 1 Department of Dermatology and Skin Aesthetics, University Medical Center at Ho Chi Minh City, Ho Chi Minh City, Vietnam 2 Department of Dermatology and Venereology, Faculty of Medicine, University of Medicine and Pharmacy at Ho Chi Minh City, Ho Chi Minh City, Vietnam Key words: Lidocaine, Infiltrative anesthesia, Dermatological procedures, VAS, Pain management, Adverse events Citation: Thanh LTV, Thong NT, Hung TQ, et al. Impact of Lidocaine Concentration on Analgesic Efficacy and Adverse Events in Dermatologic Infiltrative Anesthesia Dermatol Pract Concept. 2025;15(3):5382. DOI: https://doi.org/10.5826/dpc.1503a5382 Accepted: May 25, 2025; Published: July 2025 Copyright: ©2025 Le Thai et al. This is an open-access article distributed under the terms of the Creative Commons Attribution- NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing Interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding Author: Dr. Nguyen Tri Thong, Department of Dermatology and Skin Aesthetics, University Medical Center at Ho Chi Minh City, Ho Chi Minh City, Vietnam. Orcid ID: 0009-0006-3977-665X. E-mail: athendoctor@gmail.com. Introduction: Infiltrative anesthesia with lidocaine plays a vital role in pain management during dermatological procedures, ensuring patient comfort throughout the process. Objective: We aimed to investigate the correlation between three different concentrations of lidocaine (2% lidocaine with 1:100,000 epinephrine diluted at ratios of 1:2, 1:4, and 1:6) used in infiltrative anesthesia and their analgesic efficacy and adverse effects in dermatological procedures. Methods: This study employed a randomized design, with 240 patients assigned to receive varying concentrations of lidocaine with epinephrine (2% lidocaine with 1:100,000 epinephrine diluted at ra- tios of 1:2, 1:4, or 1:6) during seven common dermatological procedures: punch biopsy, excisional bi- opsy, CO2 laser biopsy, surgical excision, CO2 laser excision, fractional CO2 laser treatment, and filler injection. Total lidocaine dosage and patient comfort assessments were recorded for each participant. Results: All three lidocaine concentrations demonstrated comparable analgesic efficacy during the procedures, as measured by visual analog scale scores. The 1:6 dilution group required a sig- nificantly lower lidocaine dose, with a 39.3% reduction compared to the 1:4 dilution group and a 75.3% reduction compared to the 1:2 dilution group (P<0.001). The 1:6 dilution group experienced ABSTRACT 2 Original Article | Dermatol Pract Concept. 2025;15(3):5382 Introduction Effective analgesia in dermatological procedures is para- mount to ensuring patient comfort and optimizing treatment outcomes. Infiltrative anesthesia with lidocaine is a mainstay technique for pain management in this setting. While mini- mizing the total dose of lidocaine is desirable to mitigate po- tential systemic toxicity [1], definitive guidelines regarding the minimum effective concentration for adequate analgesia in dermatological procedures are lacking. Recent evidence from a comparative study evaluating 1% lidocaine with epinephrine versus 0.5% lidocaine with epi- nephrine in Mohs micrographic surgery demonstrated com- parable analgesic efficacy, with the 0.5% formulation using half the lidocaine dosage [2]. However, no study has yet in- vestigated the comparative analgesic efficacy of different li- docaine concentrations in other dermatological procedures. This research aimed to determine the optimal lidocaine concentration for infiltrative anesthesia in various derma- tological procedures, balancing maximal analgesic efficacy with the minimization of potential adverse effects. Objective This study aimed to investigate the correlation between dif- ferent lidocaine concentrations (2% lidocaine with 1:100,000 epinephrine diluted to 1:2, 1:4, and 1:6) and their analgesic efficacy and adverse effects in infiltrative anesthesia for der- matological procedures. The objective was to identify the optimal lidocaine concentration that maximized pain relief while minimizing adverse effects, thereby enhancing patient comfort and satisfaction during dermatological procedures. Methods Participants The investigation was a randomized controlled trial (RCT) with randomized allocation and single-blind evaluation. A total of 240 patients aged 18 years and older presenting for dermatological procedures for which infiltrative anesthesia is used were included in the investigation, with the patients blinded as to their treatment assignment. This research was conducted at the Dermatology - Skin Aesthetics Department of the University Medical Center at Ho Chi Minh City, a ter- tiary hospital in southern Vietnam, between November 2023 and June 2024. All participants were provided with compre- hensive information regarding the study’s aims, methodol- ogy, and potential risks, and written informed consent was obtained prior to enrollment. The study was approved by the Institutional Review Board of the University of Medi- cine and Pharmacy at Ho Chi Minh City (No. 1014/HĐĐĐ- ĐHYD, dated October 20, 2023). The following criteria led to patient exclusion: (i) con- current use of topical anesthesia at the site of infiltrative anesthesia administration; (ii) significant respiratory disease, hepatic pathology, or renal insufficiency; (iii) myocardial in- farction within the preceding six months, or diagnosed or currently treated arrhythmia; (iv) history of chronic pain; (v) psychiatric disorders; (vi) history of regular use of anal- gesics, anxiolytics, or antidepressants; (vii) history of allergy to lidocaine or other local anesthetics. Procedure Seven dermatological procedures were performed in this study: (i) punch biopsy; (ii) excisional biopsy; (iii) CO2 la- ser biopsy; (iv) surgical excision; (v) CO2 laser excision; (vi) fractional CO2 laser; (vii) filler injection. All anesthetic injections and dermatological procedures were administered by the blinded principal investigator. The infiltrative anes- thetic solution consisted of 2% lidocaine with 1:100,000 epinephrine diluted with 0.9% sodium chloride solution to achieve dilutions of 1:2, 1:4, or 1:6. Group A received a 1:2 volumetric dilution (one part 2% lidocaine with 1:100,000 epinephrine to one part 0.9% sodium chloride), resulting in a final concentration of 10 mg lidocaine per mL. This refers to volumetric dilution, not a percentage concentration. Group B received a 1:4 volumetric dilution (one part 2% lidocaine with 1:100,000 epinephrine to three parts 0.9% sodium chloride), resulting in a final concentration of 5 mg lidocaine per mL. This refers to volumetric dilution, not a percentage concentration. Group C received a 1:6 volumetric dilution (one part 2% lidocaine with 1:100,000 epinephrine to five parts 0.9% significantly less pain during injection than that of the 1:4 dilution group and the 1:2 dilution group (P<0.001). Conclusion: Lidocaine 2% with 1:100,000 epinephrine at dilutions ranging from 1:2 to 1:6 for infiltrative anesthesia in dermatological procedures provided similar analgesic efficacy. Importantly, the 1:6 dilution significantly reduced both injection pain and total lidocaine dosage. More studies are required to confirm our results. Original Article | Dermatol Pract Concept. 2025;15(3):5382 3 sodium chloride), resulting in a final concentration of ap- proximately 3.3 mg lidocaine per mL. This refers to volumet- ric dilution, not a percentage concentration. To ensure randomization, a researcher not involved in patient care utilized the random number generator function in Microsoft Excel software to randomly assign participants to Group A, B, or C. Patients received an initial infiltrative anesthetic injection with a volume determined by the treat- ing physician to ensure adequate analgesia for the specific procedure. The researcher recorded patient information and assigned patients to the corresponding lidocaine concentra- tion groups (Figure 1). All diluted solutions were stored in the same room temperature environment. Infiltrative anes- thesia was administered using a 30 G needle with a length of 13 mm. Immediately after injection (approximately 5–10 seconds), patients were asked to rate their pain level using a visual analog scale (VAS). Approximately one minute after the administration of infiltrative anesthesia, the designated procedure was performed. The duration of the procedure was recorded. If, during the procedure, a patient reported pain or exhibited signs of discomfort, the treating physician could administer additional anesthesia until the patient confirmed adequate pain relief. Both the initial and additional anesthetic volumes were recorded and converted to the corresponding lidocaine dosages. Following the procedure, patients were again asked to rate their pain level during the procedure using the VAS. All local and systemic adverse effects were documented for up to 60 minutes post-lidocaine administration. In summary, the following variables were recorded: age, sex, height, weight, anatomic site of the procedure, treatment area size, type of procedure, procedure dura- tion, initial anesthetic volume, additional anesthetic volume (if applicable), lidocaine dose, VAS score for pain during the procedure and during anesthetic injection, local adverse effects (if any: erythema, edema, ecchymosis), and systemic adverse effects (if any: allergic reaction, local anesthetic sys- temic toxicity). Figure 1. Patient flow. 4 Original Article | Dermatol Pract Concept. 2025;15(3):5382 An effect size (ES) of 0.49, classified as small effect according to Cohen’s effect size classification [9], was chosen to en- hance the precision and reliability of the study results. Based on these parameters, the calculated sample size per group was 80 patients, resulting in a total sample size of 240 pa- tients for the entire study. Categorical variables (sex, anatomic site of the proce- dure, type of procedure, VAS score categorizations) are pre- sented as percentages. Non-normally distributed continuous variables (treatment area size, procedure duration, volume of anesthetic used, lidocaine dose, VAS scores) are presented as median and interquartile range. Normally distributed continuous variables are presented as mean and standard deviation. Chi-squared or Fisher’s exact tests were used to examine the association between categorical variables and lidocaine concentration groups. The non-parametric Kruskal-Wallis test was employed to compare the three non-normally dis- tributed group means. Logistic regression models were uti- lized to evaluate the association between binary dependent variables (“pain” or “no pain” based on VAS score categori- zations) and independent variables (lidocaine concentration groups). Statistical significance was defined as P< 0.05. Results Between November 2023 and June 2024, 240 patients un- dergoing dermatological procedures received infiltrative anesthesia as part of this study. The mean age of the study participants was 39.9 ± 15.4 years. The majority of partic- ipants were female (61.7%). The mean height and weight of the participants were 1.61 ± 0.08 m and 58.8 ± 10.5 kg, respectively. There was no statistically significant difference in age, sex, height, or weight between the three study groups (Table 1). A total of 12 anatomical locations were recorded as sites for procedures involving infiltrative anesthesia in this study (Table 2). The most common procedure location was the face, accounting for 51.7% of all procedures. The median treatment area size was 16 mm², with an interquartile range of 10.1 mm² to 43.2 mm². CO2 laser excision was the most frequently performed procedure, representing 54.6% of all procedures. The median procedure duration was three min- utes, with an interquartile range of 2–4 minutes (Table 2). There was no statistically significant difference in procedure location, treatment area size, procedure type, or procedure duration between the three study groups. No participant required supplemental anesthesia in any of the study groups. Therefore, the initial anesthetic volume administered was the total anesthetic volume utilized. While the median anesthetic volumes used in groups A (0.4 ml), B (0.33 ml), and C (0.3 ml) showed some variation, this Outcome Measures The primary outcome of this study was the analgesic efficacy of the different lidocaine concentrations, assessed by the to- tal lidocaine dose administered and the achieved level of pain control during the procedure. Pain control was evaluated us- ing both subjective (VAS score during the procedure) and ob- jective (volume of additional anesthesia required) measures. Secondary outcomes included adverse effects associated with infiltrative anesthesia, encompassing pain during injection (assessed by VAS score during injection), other local adverse effects, and any systemic adverse effects. The VAS for pain assessment consists of a 100 mm hor- izontal line with “no pain” anchored at 0 point and “worst imaginable pain” at 100 [3]. Patients marked the line to indi- cate their subjective pain intensity during the procedure [3]. The VAS was selected for this study due to its extensive use in clinical research, established validity and reliability [4-7], and continuous scale, which allows for ratio comparisons of pain scores [8]. Bijur et al. (2001) demonstrated that 90% of paired VAS measurements for acute pain were consistent within 9 mm and suggested that a change of 10 mm or more on the 100 mm scale likely represents a clinically significant difference in pain intensity [5]. In a randomized trial investigating lidocaine dosing during dermatological surgery, Morganroth et al. (2009) found that 90.4% of patients reported VAS scores ≤10 mm, a threshold interpreted as indicative of no pain based on both subjective pain ratings and objective parame- ters such as the volume of rescue anesthesia administered [2]. Collectively, these findings support the use of a VAS score ≤10 mm as a valid cutoff to define the absence of pain. Ac- cordingly, in the present study, participants were categorized as having “no pain” if their VAS score was ≤10 mm, and as having “pain” if the score exceeded this threshold. Statistical Analysis To estimate the sample size required to compare the mean lidocaine dose used in infiltrative anesthesia across three groups (2% lidocaine with 1:100,000 epinephrine diluted at ratios of 1:2, 1:4, and 1:6) for dermatological procedures, we employed the formula for comparing multiple means. ( ) α β α− − − + − ≥ + − + + − 2 2 1 1 1 2 2 2 (z Z ) Z 1 n 1 1 ( ) 2(1 1) g g ES g Where: • n: sample size per group • g: number of groups (g=3) • α: probability of type I error (α=0.05) • β: probability of type II error (β=0.2) • ES: effect size Original Article | Dermatol Pract Concept. 2025;15(3):5382 5 Table 1. Participants’ Characteristics (n=240). Variable All patients Group A Group B Group C p-value1(N=240) (n= 80) (n= 80) (n=80) Age (years)† 39.9 ± 15.4 39.5 ± 14.2 40.6 ± 17.1 39.5 ± 15 0.98 Sex‡ Male 92 (38.3) 31 (38.8) 29 (36.3) 32 (40) 0.88 Female 148 (61.7) 49 (61.3) 51 (63.7) 48 (60) Weight (kg) † 58.8 ± 10.5 58 ± 9.4 59.6 ± 11.7 58.8 ± 10.3 0.84 Height (m) † 1.61 ± 0.08 1.61 ± 0.08 1.61 ± 0.08 1.61 ± 0.08 0.72 † Data presented as mean ± standard deviation (SD). ‡ Data presented as number and percentage [No. (%)]. 1p-value calculated using one- way ANOVA for continuous variables and the chi-squared test for categorical variables. Table 2. Characteristics of the Treatment Area and Performed Procedure (n=240). Variable All Patients Group A Group B Group C p-value1(N=240) (n=80) (n=80) (n=80) Procedure Location‡ 0.49 Head (%) 4 (1.7) 1 (1.3) 1 (1.3) 2 (2.5) Face (%) 124 (51.7) 38 (47.5) 45 (56.3) 41 (51.2) Neck (%) 9 (3.8) 2 (2.5) 1 (1.3) 6 (7.5) Chest (%) 5 (2.1) 2 (2.5) 1 (1.3) 2 (2.5) Abdomen (%) 10 (4.2) 2 (2.5) 5 (6.3) 3 (3.8) Back (%) 17 (7.1) 8 (10.0) 4 (5.0) 5 (6.3) Arm (%) 16 (6.7) 5 (6.3) 3 (3.8) 8 (10.0) Hand (%) 8 (3.3) 3 (3.8) 1 (1.3) 4 (5.0) Finger (%) 18 (7.5) 8 (10.0) 6 (7.5) 4 (5.0) Leg (%) 19 (7.9) 8 (10.0) 9 (11.3) 2 (2.5) Foot (%) 5 (2.1) 1 (1.3) 3 (3.8) 1 (1.3) Toe (%) 5 (2.1) 2 (2.5) 1 (1.3) 2 (2.5) Treatment Area Size (mm²)† 16 (10.1–41.3) 16 (9.0–36.3) 16 (9.6–36.5) 17.5 (14.1–51.5) 0.45 Procedure Type‡ 0.43 Punch biopsy (%) 65 (27.1) 24 (30.0) 23 (28.7) 18 (22.5) Excisional biopsy (%) 27 (11.3) 11 (13.8) 10 (12.5) 6 (7.5) CO2 laser biopsy (%) 4 (1.7) 2 (2.5) 1 (1.3) 1 (1.3) Surgical excision (%) 10 (4.2) 1 (1.3) 5 (6.3) 4 (5.0) CO2 laser excision (%) 131 (54.6) 42 (52.5) 40 (50.0) 49 (61.3) Fractional CO2 laser (%) 1 (0.4) 0 (0.0) 1 (1.3) 0 (0.0) Filler injection (%) 2 (0.8) 0 (0.0) 0 (0.0) 2 (2.5) Procedure Duration (min)† 3 (2–4) 3 (2–4) 3 (2–4) 3 (2–4) 0.38 †Data presented as median (interquartile range). ‡Data presented as number and percentage [No. (%)]. 1p-value calculated using the Kruskal-Wallis test for continuous variables (e.g., treatment area size and procedure duration) and the chi-squared test for categorical variables (e.g., procedure location and type). difference was not statistically significant (P=0.7). However, the median lidocaine doses in groups A (4 mg), B (1.63 mg), and C (0.99 mg) differed substantially. Notably, group C re- ceived a significantly lower lidocaine dose compared to both group B (39.3% lower) and group A (75.3% lower). This difference in dosage was statistically significant (P<0.001) (Table 3). Across all three study groups, the vast majority of par- ticipants (97.5%, or 234/240) reported minimal to no pain (VAS score ≤10) during the procedure. While the proportion of participants reporting “no pain” varied slightly across the groups–95% (76/80) in group A, 97.5% (78/80) in group B, and 100% in group C–this difference was not statistically significant (P=0.17) (Table 3). 6 Original Article | Dermatol Pract Concept. 2025;15(3):5382 Table 3. Comparison of Anesthetic Volumes, Lidocaine Doses, and Pain Outcomes Across Groups (n=240). Variable Group A Group B Group C p-value1(n=80) (n=80) (n=80) Anesthetic volume (mL)† 0.4 (0.2–0.5) 0.33 (0.2–0.55) 0.3 (0.15–0.6) 0.7 Lidocaine dose (mg)† 4 (2–5) 1.63 (1–2.75) 0.99 (0.5–1.98) <0.001 Procedural pain (VAS Score)‡ 0–10 (No Pain) (%) 76 (95.0) 78 (97.5) 80 (100) 0.1711–20 (%) 3 (3.8) 2 (2.5) 0 (0) 21–30 (%) 1 (1.2) 0 (0) 0 (0) Injection pain (VAS Score) Median VAS Score (mm) † 29.9 (17.6–48.7) 15 (9.1–22.2) 2 (0–4.4) <0.001 Categories of injection pain (VAS Score) ‡ 0–10 (No Pain) (%) 4 (5.0) 24 (30.0) 69 (86.3) < 0.001 11–20 (%) 24 (30.0) 30 (37.5) 10 (12.5) 21–30 (%) 12 (15.0) 18 (22.5) 0 (0) ≥31 (%) 40 (50.0) 8 (10.0) 1 (1.3) † Data are presented as median (interquartile range). ‡ Data are presented as number and percentage [No. (%)]. 1p-value calculated using the Kruskal-Wallis test for continuous variables (e.g., anesthetic volume and injection VAS scores) and the chi-squared test for categorical variables (e.g., pain intensity categories). The sole adverse effect observed among participants was pain experienced during the administration of lidocaine; no other local or systemic adverse effect was reported. A statis- tically significant difference (P<0.001) in pain scores was observed, with group C exhibiting an 86% and 93% reduc- tion in VAS scores (2 mm) compared to group B (15 mm) and group A (29.9 mm), respectively (Table 3). Group C also exhibited a significantly higher proportion (P<0.001) of par- ticipants reporting “no pain” (VAS score ≤10) during injection (86.3%) compared to group A (5%) and group B (30%) (Table 3). Moreover, the odds of experiencing “pain” (VAS score >10) during injection were significantly elevated for group A (OR = 119.2, 95% CI: 36.3–391.7, P<0.001) and group B (OR = 14.6, 95% CI: 6.6–32.4, P< 0.001) relative to group C. Discussion Although previous research has compared the analgesic ef- ficacy of different local anesthetics for infiltrative anesthe- sia [10] as well as the total lidocaine dose required for two different lidocaine concentrations (1% and 0.5%) in Mohs surgery [2], this study contributes to the literature by in- vestigating the relationship between different dilutions of 2% lidocaine (1:2, 1:4, and 1:6) used in infiltrative anesthe- sia and the analgesic efficacy and adverse effects (specifically pain on lidocaine injection) across seven different dermato- logical procedures. Lidocaine concentration is the primary determinant of dosage for any given volume. To mitigate the risk of dose-dependent adverse effects, including potentially life-threatening complications associated with lidocaine toxicity, clinicians should prioritize achieving adequate an- esthesia with the lowest effective dose. Furthermore, a lower lidocaine concentration appears to reduce pain during anes- thetic injection, thereby improving patient comfort during infiltrative anesthesia administration [11-12]. Group C (2% lidocaine diluted 1:6) utilized a compara- ble volume of anesthetic to group A (2% lidocaine diluted 1:2) and group B (2% lidocaine diluted 1:4) while main- taining effective analgesia throughout the procedures. The absence of a need for additional anesthetic suggests that the procedures were either painless or that any pain experienced was minimal and tolerable. This observation provides an ob- jective measure of the effectiveness of the anesthetic, com- plementing the subjective assessment of pain using the VAS. The median lidocaine dose used in this study was 1.98 mg, with 75% of cases using less than 3.45 mg. The highest dose used was 20 mg, which is considerably lower than the rec- ommended maximum dose of 500 mg for lidocaine with epinephrine for infiltrative anesthesia in adults [1]. When 400 mg of lidocaine is administered via infiltrative injection, the peak plasma lidocaine concentration reaches 1 μg/mL with a 1:200,000 epinephrine solution after approximately 15 minutes [13-16]. At plasma lidocaine concentrations of 1–5 μg/mL, the initial symptoms of lidocaine toxicity, such as tinnitus, dizziness, circumoral and fingertip paresthesia, dip- lopia, metallic taste, anxiety, and agitation, may appear [17]. The results of this study demonstrate that the lidocaine doses used for infiltrative anesthesia in the included procedures were far below the threshold for toxicity and likely very safe. Furthermore, the lidocaine dose used in group C (median Original Article | Dermatol Pract Concept. 2025;15(3):5382 7 injection revealed that patients in group A were 119.2 times more likely to report pain during injection (VAS >10) compared to group C. Similarly, patients in group B were 14.6 times more likely to report pain during injection com- pared to group C. The p-value of < 0.001 indicates that these results are highly statistically significant. This analysis demonstrates a strong correlation between lidocaine concen- tration and pain experienced during infiltrative anesthesia. As in previous studies worldwide, due to resource lim- itations, we were unable to measure plasma lidocaine con- centrations. Various factors can influence systemic lidocaine levels, such as injection site vascularity and individual differ- ences in hepatic metabolism and renal excretion. However, throughout the study period, no patient exhibited signs of lidocaine toxicity, and the doses used were significantly be- low known toxic thresholds. In addition, the study has several other limitations. First, we did not perform longer-term follow-up beyond 60 minutes post-procedure, which may have limited detection of delayed adverse events. Second, although all assessments and data collection were conducted by a single principal investigator, infiltrative anesthesia was administered by multiple treating physicians. While standard injection protocols were followed, minor variations in technique, such as needle angle, depth of insertion, injection speed, and tissue resistance, may have contributed to differences in pain perception among patients. However, all treating physicians were senior dermatologists with substantial experience at major tertiary hospitals in Vietnam, which likely minimized inter-operator variability. Finally, this study was conducted in a single tertiary dermatol- ogy center in Vietnam, and all participants were Vietnamese patients undergoing dermatological or cosmetic procedures. Therefore, the generalizability of our findings to other popu- lations, ethnic groups, or clinical settings may be limited. Conclusion In summary, the use of 2% lidocaine with 1:100,000 epi- nephrine at dilutions ranging from 1:2 to 1:6 for infiltrative anesthesia in dermatological procedures provided similar analgesic efficacy across seven types of dermatological pro- cedures in this study. However, lower concentrations, partic- ularly the 1:6 dilution, minimized pain during injection and reduced the required lidocaine dose. Future studies could in- vestigate even lower dilutions of lidocaine with epinephrine to further explore the optimal concentration for infiltrative anesthesia in dermatologic and cosmetic procedures. Ethics Approval: The study was approved by the institu- tional ethics committee (No. 1014/ HĐĐĐ-ĐHYD, dated 20-Oct-2023). 0.99 mg) was approximately 39.3% lower than in group B (median 1.63 mg) and 75.3% lower than in group A (median 4 mg). This reduction in lidocaine dosage can provide cost benefits and potentially decrease the risk of toxicity in pro- cedures requiring larger areas of anesthesia. The results demonstrate excellent analgesic efficacy across all three groups, with 97.5% of patients reporting “no pain” (VAS ≤10) during the procedures. This indicates effective pain control, with patients experiencing minimal to no pain throughout the procedures (the proportion of patients report- ing “no pain” in groups A, B, and C was 95%, 97.5%, and 100%, respectively). These findings are consistent with the pre- viously mentioned objective pain assessment, where no partici- pant in any of the three groups required additional anesthesia. Group C exhibited the lowest median VAS pain score during anesthetic injection (2 mm), followed by group B (15 mm) and group A (29.9 mm). This suggests that patients in group C generally experienced less pain during infiltrative anesthesia compared to the other two groups. Specifically, the median VAS pain score during injection in group C was approximately 86% lower than in group B and 93% lower than in group A, indicating a significant difference in pain levels between the groups. Furthermore, group C also had the highest proportion of patients who reported “no pain” (VAS ≤10) during injection at 86.3% (95% CI: 78.8%–93.5%). Group B had a lower proportion of pain-free injections at 30% (95% CI: 19.7%–40.3%), while group A had the low- est at 5% (95% CI: 1.1%–10.1%). This difference was sta- tistically significant (P<0.001), indicating a real difference in the proportion of pain-free injections between the groups. The significantly higher proportion of pain-free injections in group C compared to groups A and B suggests that the lido- caine concentration used in group C may be more effective in reducing pain during infiltrative anesthesia. This finding may be related to the pH of the diluted lidocaine solution. A highly acidic solution can cause more pain during local an- esthesia. According to a previous study by Simon Frank, the average pH of a 1% lidocaine solution with 1:100,000 epi- nephrine was 4.24 ± 0.42, while a 2% lidocaine solution with 1:100,000 epinephrine had an average pH of 3.93 ± 0.4 [18]. Although the pH of more diluted solutions was not reported, it is reasonable to hypothesize that increasing dilution may lead to a higher pH and, consequently, less pain on injection. However, the pH of the diluted lidocaine solutions was not measured in our study. The proposed mechanism link- ing lidocaine dilution and reduced injection pain is therefore speculative and based solely on inference from previously published data. Future studies are warranted to directly in- vestigate the relationship between lidocaine dilution, solu- tion pH, and pain perception during infiltration. Logistic regression analysis evaluating the impact of lidocaine concentration group on pain during anesthetic 8 Original Article | Dermatol Pract Concept. 2025;15(3):5382 9. Samritin S, Purnama B, Ulfah M. A meta-analysis study of the effect of the blended learning model on students’ math- ematics learning achievement. Jurnal Elemen. 2023;9(1):16. DOI:10.29408/jel.v9i1.6141 10. Howe NR, Williams JM. Pain of injection and duration of an- esthesia for intradermal infiltration of lidocaine, bupivacaine, and etidocaine. J Dermatol Surg Oncol. 1994;20:459-64. PMID: 8034840 . DOI: 10.1111/j.1524-4725.1994.tb03216.x 11. Vent A, Wu Y, Ghadially R, et al. 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